The roto-zip is beefier, but it's also a bit unwieldy IMO...just not as easy to use for ultra fine detail work as a dremel is.

To put it in perspective, I can freehand a perfect (as in hole saw perfect) 120mm hole into 16ga sheet aluminum with relative ease on a dremel...I do go through drums and discs like mad however.

The flex-shaft for dremel IMO is almost worthless. I only use it when I can't fit the dremel tool into that area reasonably.

Oh, and buy a big kit as soon as possible...if you get the dremel branded one, get the kit with the circular mini-saw...I found it very useful for cutting through the fiberboard backs of cheap furniture/desks and such. The cube furniture I bought from target I'm using as an A/V stand has a nice cutout in the back I made with that mini-saw...took less than 3 minutes.

Rotozip can be a little tough to control compared to a dremel or a jig saw, but it does cut pretty fast. I was working in the tool department at Sears when they came out, and they were a pretty hot selling item. Definitely not as hot as the Gearwrench, though.

"The internet is a place where absolutely nothing happens. You need to take advantage of that." ~ Strong Bad

For routing style tasks, plunging and edging, high rpms are de rigeur. The purpose is to get a smoother finished cut. If you look at the pro dremel style tools for metal, they tend to spin at around 30,000.